1. Field of the Invention
The present invention relates to a vehicle wiper device for an openable window glass, in particular, applicable to vehicles in which the wiper device is in wiping contact with a glass of an openable rear window (glass hatch type vehicles).
2. Description of Related Art
Recently, there are vehicles such as station wagon or hatchback type vehicles in which a rear window glass at the tailgate is openable independently of an openable rear door for loading luggage. A conventional wiper device has been attached directly to the rear window glass for wiping a surface of the glass.
However, among component parts constituting the wiper device, an actuator is, in particular, heavy and bulky. Thus, a large operation force for opening the rear window is required. On the other hand, when the rear window is abruptly closed to hit the rear door with a large impact, the glass may be strongly stressed at a portion where the actuator is fixed so that the glass may be broken. Further, as the wiper device having the actuator is large, the wiper device is likely to interrupt the rear view. Furthermore, it becomes relatively complicated to supply an electric power to a wiper motor, as a power source of the actuator, in case that the actuator is fixed to the window glass.
To cope with these drawbacks, there has been proposed a wiper device in which the actuator is fixed to the rear door and the pivot shaft to be concentrically fixed with a wiper arm is rotatably held by the window glass such that the pivot shaft may be engaged with and driven by the actuator only when the window is closed.
In the wiper device mentioned above, the actuator power source drives a disk plate mounted on an output shaft thereof to reciprocatingly rotate within a predetermined rotation angle. The disk plate is provided with a connecting hole at a position radially outwardly offset from a center axis of the output shaft. On the other hand, the pivot shaft is rotatably held in a pivot holder secured to the window glass so as to be concentrically with the output shaft. A lever is fixed to an end of the pivot shaft on a side of the actuator and the lever is provided with a connecting pin to be fitted into the connecting hole of the disk plate.
When the window is closed and the connecting pin is fitted into the connecting hole, the disk plate and the lever are engaged with each other so that the driving force of the actuator may be transmitted to the pivot shaft. The oscillation movement of the disk plate within the predetermined rotation angle according to an operation of the actuator power source causes the lever to simultaneously oscillate so that the pivot shaft may be rotated to make the wiper arm move within the predetermined rotation angle and make a wiper blade attached to a leading end of the wiper arm move through an arcuate path on the widow glass surface.
However, the wiper device has a problem that, when the window is opened, at least a part of the disk plate is exposed out of a window aperture because of the construction that the disk plate and the lever are engaged with each other on closing the window. From the foregoing, the oscillation movement of the disk plate according to the operation of the actuator even when the window is kept opened does not give a driver or operator a favorable feeling.
On the other hand, when the widow is closed during the operation of the actuator, the oscillation movement of the disk plate brings frictional noises, unusual loads or resistance on engaging the connecting pin with the connecting hole.
For the purpose of the problem, it may be contemplated to incorporate a switch in the wiper motor electrical circuit such that opening the window may open the switch to break the wiper motor circuit and closing the window may close the switch to complete the wiper motor circuit. As a result, the actuator is driven only when the window is closed and, that is, only when the switch is closed. However, with the wiper device mentioned above, the driver or operator may be surprised and may not have a favorable feeling by a sudden movement of the wiper arm and blade starting as soon as the window is closed and, simultaneously, the switch is closed.